I don't know. I think many 4 stroke scooters are relatively dirty as well. I like to remind people that gumdrops and perfume doesn't come out of the tail pipe of their 4 stroke scooter. It's that motorcycles aren't held to as strict of a standard for nitrogen gases and particulate (yes, even 4 stroke belch particles of unburned soot). It goes for all two wheelers. They get great gas mileage and carbon emissions are directly related to the amount of fuel used, but it's not the whole story. Cars used to get as good or better gas mileage 20 years ago. Remember the Festiva getting better mileage than a Prius and the GM 3.8 L FI engine in Olds and Buicks that got high 20's in the city and low to mid 30s on the highway while making great power? But those same cars probably wouldn't pass emissions testing today.

I have yet to read an article with accurate statements regarding the issue. Few cite how 2 wheelers in general make up what ends up to be a rounding error of a percentage of total emissions for stationary and mobile energy production (and even a tiny percentage for all mobile emissions). And they don't account for life-cycle costs such as production, shipping, disposal and that motorcycles end up resulting in less crank case oil burned after it's disposed of. Articles like that are perfect for the average lifestyle section reader that usually doesn't finish the article let alone think critically about the subject.

I agree that all four-strokes are not equal. I suspect that my 2002 Bajaj is not as clean as it used to be, now that I have a pipe on it and have mucked with the carb jetting.

But the new Euro 3 emission compliant scooters are trickling in. With the fuel injection and controls they got to be better yet. Vespa GTS is in this category. My buddy just bought a Daelim S1 125 with fuel injection from Blue Cat. Kymco and Yamaha FI scooters are coming.

It's kind of a bummer that the world doesn't agree on gas formulation and emission standards. It's got to be costly for manufacturers and we don't get all of the good stuff, like the 3 cylinder turbo-diesels from Volkswagon that get 70 mpg.

It seems that it is not what comes out of the rear end, but how much comes out fo the rear end. Pound for Pound, an SUV that only gets 15 mpg is still no comparison to a scooter that gets 65 mpg or better. It's as much a matter of consumption as it is the pollution control gadgetry. I would think two strokes consume oil the same as a worn out motor that burns it past the pistons, cylinder liners, and leaky valve stems.

_________________If there are any parts on the road behind me, pick 'em up, I may need 'em real soon.

Another topic that goes unreported and unconsidered is the fate of the liter of oil that comes out of the 4 stroke scooter at the time of an oil change. Or the 5 or 6 quarts that come out of an auto. Often the waste oil is burned in a totally unregulated industrial furnaces or (for instance) a tug boat engine....
Todays two strokes are regulated by EPA on the front side and provide nothing for reburn on the backside.

Burnable waste chemicals are processed and blended for use as fuel for cargo ships and other large industrial powerplants. Nothing new, and limited pollution controls once the blended fuel heads out to sea. Waste oil burners are as clean burning as a garbage dump on fire. Now that fuel prices are up, those drums full of oil change waste might have some cash value which might curb the use of waste oil for heating if it's not so readily available.

_________________If there are any parts on the road behind me, pick 'em up, I may need 'em real soon.

I think that emissions ratings need to take MPG into account. So you get gallon per gallon more emission from a two stroke, but if you are burning 1/5 the fuel things equal out pretty fast and the per mile cost to the rider is significantly less.

I think ideally the number of passengers should be taken into account as well so that a balanced way of comparing the apples to oranges of different vehical types might look something like tailpipe emssions/MPG/# of passengers

So that way you will have emissions per passenger MPG. This analysis helps you understand why using big stinky diesels for busses and passenger trains actually makes sense. And also why two stroke scooters aren't really that scary from a air pollution perspective. Except mine which might as well be burning coal it runs so dirty.

Emissions are typically measured per 100km, not per gallon. In other words, those numbers that show scooters to be dirtier, are already talking about mile-per-mile, not gallon-per-gallon. And yes, they're true. Scooters are good for a lot of reasons, but environmentally, they're not so good, period. No twisting or wrangling really changes that. Four-strokes are better than two-strokes by a great deal, and modern 4-stroke liquid-cooled scooter engines with EFI would surely be as clean gallon-per-gallon as modern car engines (meaning cleaner mile-per-mile), but just about anything carbureted is going to be much dirtier gallon-per-gallon than anything with GOOD EFI. Whether or not it's possible for a clean carbureted 4-stroke scooter to be cleaner mile-per-mile than a modern EFI car engine I guess comes down to a question of just HOW high the fuel mileage is, but in the general case, they're dirtier mile-per-mile.

If you look at life cycle, of course, including construction and disposal, scooters have a chance of coming out ahead - but even then I doubt 2-strokes would come out ahead of anything with EFI.

I read something years ago about the EFI systems on the then new SAAB 9000's. It used a big computer to monitor the voltage needed to keep a platinum wire (suspended in the intake track) heated to a specific temperature. The computer could calculate the mass and velocity of the air entering the engine and then inject the exact amount of fuel to burn it with maximum efficiency. I think it also monitored how the spark plugs current draw varied with each spark and used that to adjust fuel supply for the next charge too. In conjunction with the converter and other emission control stuff SAAB claimed it actually cleaned the ambient air in London when driven there.

If you look at life cycle, of course, including construction and disposal, scooters have a chance of coming out ahead - but even then I doubt 2-strokes would come out ahead of anything with EFI.

Come out ahead in what contest? Gas (as state of matter rather than fuel), particles, carbon emissions, petroleum used, financial cost? What are we concerned about here? I find it funny how some folks seem to speak from an informed point of view and state no data or facts but use phrases like, 'lots', 'greatly' and such. And keep in mind, dust settles, gases break down or are abosrbed and lots can happen in between. I have seen scant data on cradle to grave for products let alone a barrel of oil. But 'a lot' is said about snapshots in between.

My ride of choice for this season has been the Vectrix electric scooter. Until this week, I relied upon a demo from their Natl sales rep who happens to be from St Paul.
I've been aware of the Vectrix project for a few years now and wasn't at all inclined to participate.
From everything I'd heard and read, the concept seemed flawed. From price to speed to maximum range....... I just wasn't interested.
Then I rode the Vectrix. It was (and still is) the best two wheeled vehicle (no, any vehicle) I've ever ridden.
I continued to have the Vectrix as a weekend demo for a few more weeks, I have only become more addicted to its' ride and performance.
This week we received our first show room models and a Vectrix demo that I will ride every day with the choice of any Vespa, Piaggio, Kymco, or Genuine scooter available.
Please understand that I don't particularily like Maxi scooters. I never have. To embrace the Vectrix like this is really out of character for me.
I'll try to keep you all posted as the economy stays under a penney per mile. That's just sick.